B Essential Attributes

The second rule is to use a principle based on the essential attributes of the things we are classifying. An essential attribute is a fundamental one, an attribute that makes a thing what it is. If we divide a genus according to an essential attribute, we are grouping together things that are fundamentally similar and separating things that are funda-mentally different. And because a fundamental attribute underlies and explains many of a thing’s superficial attributes, things that are fundamentally similar will probably have many attributes in common; things that share a superficial, nonessential attribute may well have nothing else in common.

Let’s consider the animal kingdom once again. Biologists classify animals into the categories MAMMAL, REPTILE, AMPHIBIAN, BIRD, INSECT, etc. The principles they use include mode of reproduction (does the animal lay eggs or bear its young alive?), internal physiology (vertebrate vs. invertebrate, warm-blooded vs. cold-blooded), and means of locomotion (swimming, flying, crawling). These principles are aspects of two attributes fundamental to all forms of life: An organism must maintain itself by acting

on the environment, and it must reproduce itself. This classification of animals, then, is based on essential principles, and the advantages of the classification are obvious.

Animals that survive and reproduce in similar ways are likely to have a great deal in common and can naturally be studied as a group.

By contrast, suppose that we classify animals according to a nonessential attribute such as color:

[color]

elephants mosquitoes some sharks

brown bears some lizards wrens

some parrots other lizards praying mantis

canaries some snakes cardinals

some fish

RED BROWN GREEN YELLOW

ANIMALS

GRAY

Of course this is not a complete classification of animals, but it does indicate what’s wrong with classifying them according to this attribute. The items that are grouped together in each category have nothing else in common. The differences among ele-phants, mosquitoes, and gray sharks are much more fundamental than the superficial similarity in color. And the similarities between green and brown lizards are much more fundamental than the superficial differences in color. As a result, this classification is useless. Knowing that a certain animal belongs to one of these categories tells you al-most nothing about it. Imagine having to act on the information that a gray animal was approaching, without knowing anything else about it!

How does the distinction between essential and nonessential attributes apply to other areas? Let’s look at a few examples. The essential attribute of a man-made object is usually its function. Such objects are created to serve a purpose, and the purpose explains why they are designed the way they are. If you came across an unfamiliar tool in a museum, your first question would probably be: What’s it for? If you knew the answer to that question, then you would understand why the tool has a certain shape and internal structure, why it is made of the material it is, and so on. The same is true for human institutions. Thus, if you were studying corporations, it would be natural to classify each according to its function: Does the corporation produce goods or services?

Is it a nonprofit or for-profit organization?

In the physical sciences, essential attributes are those that underlie and explain the surface properties we can observe directly, and scientists have pushed deeper and deeper into the structure of matter in the search for these underlying causes. Ancient Greek philosophers, for example, divided matter into four elements: earth, air, water, and fire.

Modern chemists have replaced that early system with the table of elements, classifying matter according to the kinds of atoms that make it up. The properties of the atoms explain many of the observable features of matter: They explain why some elements are gases at room temperature, why metals conduct electricity, and so on. The table of ele-ments is therefore a classification by essential attributes.

1.2 Rules of Classification 17

In dealing with people, our standards for what is essential are too complex even to summarize here, but let’s look at a case in which one of these standards is applied:

the issue of discrimination. In the abstract, discrimination means noticing differences among people and classifying them into groups on the basis of those differences. We do this all the time. Teachers discriminate among students in assigning grades; employ-ers discriminate among job applicants; everyone discriminates among people in choos-ing friends. What most of us object to is not discrimination (or classification) per se, but discrimination on the basis of attributes such as race or sex that are not essentially related to the treatment a person deserves. Thus an employer who adopts an equal op-portunity policy is choosing to classify job applicants by ability, training, and character rather than by race or sex—on the ground that ability, training, and character are essen-tially related to job performance, whereas race and sex are not.

The word “essential” always has the sense of “fundamental” or “important.” But as the preceding examples illustrate, standards for what is fundamental or important vary from case to case. Identifying essential attributes may take years of research (as in science), and it always takes a good deal of thought. Unfortunately, there is no simple, mechanical rule we can follow in distinguishing essential from nonessential principles of classification. You will have to use your judgment, and you will have to accept the possibility that reasonable people may disagree. Nevertheless, the examples also indi-cate the value of looking for essential attributes: They bring clarity and coherence to the organization of our knowledge.

In addition, we need to remember that classification serves a purpose, and our pur-pose affects what we take to be essential. So far, we have taken for granted that our purpose is to understand the nature of the things being classified, on the basis of the similarities and differences among them. That is, we are considering the things as they are in themselves. In and of itself, for example, the essential attribute of a piece of fur-niture is clearly its function. But an interior designer, who is concerned primarily with aesthetic issues, may need to classify furniture by style. In relation to that specialized practical purpose, it is legitimate to regard style as essential.

EXERCISE 1.2

Evaluate each of the following classifications. First determine whether it uses a consis-tent principle and is mutually exclusive and jointly exhaustive. If it passes that test, then determine whether the principle used is essential. If it is not, try to think of a specialized purpose for which the principle might be essential.

SUMMARY

1. A single principle or set of principles should be used consistently so that the categories (species) are mutually exclusive and jointly exhaustive.

2. The principle or principles used should be essential.

❋ 1. Books: paperbacks, hardbacks, first editions

2. Medicines: antibiotics, laxatives, pills, antihistamines

3. Foods: meats, vegetables, junk food, fruits, breads

❋ 4. Movies: thrillers, Westerns, porno-graphic, foreign

5. Students: under 5 feet tall, 5 to 6 feet tall, over 6 feet tall 6. Wine: Chardonnay, red, Merlot,

French, sparkling

❋7. Sports: team, aquatic, individual, noncompetitive

8. Trees: leaf-shedding, evergreen, shade

9. Cars: economy, oversize, interme-diate, compact, standard, full-size ❋ 10. Shoes: walking, athletic, leather,

dress

11. Colors: blue, orange, warm, red, primary

12. People: those who would rather be hosts, those who would rather be guests

❋ 13. Jobs: clerical, sales, managerial, service, manual

14. Countries: developed, underdeveloped

15. Countries: free, unfree, partially free